One of the reasons Diablo II retained its popularity for such a long time was because there was always a reason to reroll.
Without respeccing, you needed to start over is you wanted to try a new build. And builds were constantly evolving. Every class had at least 2-4 viable endgame builds and new one came in as fast as old ones dissipated.
Diablo III does not have such a system. Easy respeccing means there is little to no reason to ever reroll and character.
In fact once you have one of each class leveled to 60, there's literally no reason to ever go back. Just stack a bit of alternative gear and you're set.
I may be missing something but I feel this design decision fundamentally undermines the longevity of the game, which was a big reason for Diablo IIs success.
I'm hoping that Inferno's difficulty will greatly increase the longevity and fun of the game. D2 didn't have endgame content at all - 8man H Baal runs were soloable - I doubt that will be the case with Inferno.